Arrangement for producing modulated currents



y 19, 1932- L H. GARBER ET AL 1,867,663

ARRANGEMENT FOR PRODUCING MODULATED CURRENTS Filed May 20, 1931 i l l I i l I l l lji fl i J INVENTORS zzam-erzzalzlaw BY CflZac/cwvwfi W; ATTORNEY Patented July 19, 1932 TUNITED STATES LESLIE n. GARIBER, RALPH e. HALL, AND CONOVEB, BLAcKwoon, or DENVER,- GoLo- RADO, ASSIGNORS T AMERIGAN TELEPHONE AND TELEGRAPH: COMPANY, A COR- fr} PonArIoN or NEw YORK V ARRANGEMENT FOR PRODUCING Monu ATED cam ra] 1 Application filed ma 20,

r This invention relates generally to signaling systems. More particularly, this invention relates to arrangements for producing modulated currents. Still more particularly, this invention relates to apparatus for producing modulated currents suitable for ringing purposes in telephone systems.

On long haul telephone circuits employin intermediate amplifiers, it is often of advantage to use terminal signaling equipment for ringing purposes which may be operated by alternating current having a frequency lying'within the ordinary voice range. Since the signaling current is within the voice range, the need for signal relaying equipment at the various amplifying pointsbecomes obviated and the signaling current may be passed and amplified by each amplifier in the same manner as are ordinary speech currents; e e

To insure against false operation of the signaling equipment by voice currents or other currentsnot intended for ringing purposes, it is the practiceto arrange the signaling equipment to operate only on currents which meet two frequency requirements. In this country this requirement is usually met by employing 1,000 cycle current interrupted about 20 times per second.

There has recently arisen a demand for means whereby a lineman may produce and transmit the double frequency signaling current for ringing and testing purposes. In order for equipment to be satisfactory for these purposes, it is necessary that the equipment be light in weight and small in size so that it may, for example, form'part of a telephone linemans familiar test set. l It is also important that such equipment be quite inexpensive.

This invention proposes to provide suitable arrangements for meeting the requirements set forth hereinabove. Thus, it may be stated in general that the invention involves two devices, one capable of providing current of a particular frequency and the other capable of interrupting the output of the first device at a second particular frequency.

This invention will be better understood from the detailed description hereinafter fol- 1931. Serial No. 538,824. 5

lowing when read in connection with the accompanying drawing which represents one.

embodiment of the invention-showingits essential elements merely for the purpose of illustration; 1 P a Referring to the drawing, the reference character G represents a hand generator of alternating current which may pref y be a sub-audible frequency ofpredetermined value, as for example, cycle's', but the generator G may bereplaced by any form of ap- K once for each cycle of the alternating cur rent impressed upon its winding. 7

The apparatus included within the confines of the box shown in dotted lines, repre sents an interrupter. It comprises a carbon button contact arrangement M, a coil'of wire W wound on a core ofiron, a reed A which may be made of iron or other magnetic material and which may beadjusted or tuned to vibrate at-any desired frequency as, for 6X- ample, 1,000 cycles per secondfa plunger P which need not have =magneticproperties', and a diaphragm D. The reed'Acontinu'ally rests against the plunger P and presses against the diaphragm D adjacent tojthe carbon button arrangement M. A battery desig- V nated Bsupplies the energy required to operate the interrupter. The battery'B, the winding W and the carbon button arrangement M are connected in series relationship.

When the armature of'the relay it rests energized by current which flows fronifthe battery B throughthe carbon button aragainst the contact K the winding W willgbe the pressure on the diaphragm D and there will then be a corresponding increase in the resistance of the carbon button arrangement M, and therefore a decrease in the current flowing from battery B throughthe winding W. This decrease in the current through the winding WV will reduce the attractive force of the winding V upon the reed A and, consequently, the pressure of the reed A against the diaphragm D will be increased, thereby completing one cycle of changes in the current flowing through the winding WV, as well as in the pressure-exerted on the diaphragm D. The continued repetition of this cycle will result in a steady vibration of the reed A at a constant frequency, and an alternating current electromotive force having the same frequency as the reed A will be set up across the terminals of the carbon button contact arrangement M, which are designated T and T If the reed A vibrates at 1,000 "cycles per second, the voltage variations of the carbon button contact arrangement M will occur at the same frequency.

A line designated O is connected to the ter- I minals T and T of the carbon button contact arrangement M through a retard coil L and a condenser C. The condenser C primarily prevents direct current originating at the battery B from being applied to the circuit 0. The coil L presents a desired amount of inductance or impedance for the circuit 0, yet it will be understood that under certain conditions, especially where additional inductance or impedance is not required, the coil L may be dispensed with.

The vibrator produces alternating current variations as long as the contact K is closed by the armature of the polar relay R. Inasmuch as the armature of the relay R is periodically closed in accordance with the frequency of the alternating current impressed upon its winding by the generator G, the al ternating variations of the vibrator will be interrupted at the frequency of the armature of the relay R. If the armature of the relay R is vibrated at, for example, about 20 cycles per second, and assuming'the frequency of V the vibrator to'be 1,000 cycles per second, there will be transmitted to the circuit 0 current of 1,000 cycles per second interrupted 20 times per second which-will operate the ringing or other equipment at the other end of the line. The generator G is obviously a hand operated device having a crank, operatin'g' ears which rotate an armature at any desired speed. This crank may, for example, be operated so as to rotate the armature at '20 revolutions per second.

While this invention has been shown and ing from the spirit of the invention and the scope of the appended claims.

What is claimed is:

1. In a portable test set, the combination of a polar relay, a source of current of one frequency connected to the winding of the polar relay, an interrupter, a source of direct current connected to said interrupter for producing alternating current variations at a second frequency, and means interconnecting the armature of the polar relay'and said interrupter for producin current of the second frequency'interrupted in accordance with the first frequency.

2. In a portable test set, the combination of a polar relay, an interrupter which includes a winding, a reed, a carbon buttonof variable resistance, a diaphragm controlling the resistance of the carbon button, and a plunger separatingthe reed from the diaphragm, and a source of direct current connected in series with the armature and one of the contacts of said polar relay aswell as with the winding and the carbon button of said interrupter.

In a portable test set, the combination of a polar relay, a hand generator connected to the winding of the polar relay and transmitting a low frequency alternating current,

an interrupter which includes a winding, a

magnetic reed a carbon button of variable resistance, a diaphragm controllingthe re? sistance of the carbon button, and a plunger interposed between the reed and the diaphragm, a source of direct current connected in series with the armature of the polar relay and one of its contacts aswell aswith the winding and the carbon button of the interrupter,and a line connected across the cark bon button of the interrupter. a V

In testimony whereof we have signed .our names to this specification this 12th day of May, 1931.

LESLIE H. GARBER.

RALPH G. HALL.

.GONOVER BLACKVVOOD.

described in certain particular arrangements 1 merely for the purpose 'of'illustration, it will be understood that thegeneral principles of this invention may be applied to other'and widely variedforgani'zations without depart.- 

